content: Add an overridable task runner to ChildThreadImpl

content/child/child_thread_impl.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_CHILD_CHILD_THREAD_IMPL_H_
 #define CONTENT_CHILD_CHILD_THREAD_IMPL_H_
 
 #include <string>
 
 #include "base/basictypes.h"
@@ skipping 63 matching lines @@
   // must be terminated before Shutdown returns. In particular, if a subsystem
   // has a thread that post tasks to ChildProcess::main_thread(), that thread
   // should be joined in Shutdown().
   ~ChildThreadImpl() override;
   virtual void Shutdown();
 
   // IPC::Sender implementation:
   bool Send(IPC::Message* msg) override;
 
   // ChildThread implementation:
+  // Returns the task runner which should be used to post tasks to run on this
+  // child thread. Note that this may be different from the underlying message
+  // loop returned by message_loop(). For this reason, only use message_loop()
+  // if you need to directly manipulate the underlying message loop, e.g., by
+  // adding a task listener instead of just posting tasks for execution.
+  virtual scoped_refptr<base::SingleThreadTaskRunner> GetTaskRunner();
 #if defined(OS_WIN)
   void PreCacheFont(const LOGFONT& log_font) override;
   void ReleaseCachedFonts() override;
 #endif
 
   IPC::SyncChannel* channel() { return channel_.get(); }
 
   MessageRouter* GetRouter();
 
   // Allocates a block of shared memory of the given size. Returns NULL on
@@ skipping 65 matching lines @@
   }
 
   QuotaMessageFilter* quota_message_filter() const {
     return quota_message_filter_.get();
   }
 
   ChildResourceMessageFilter* child_resource_message_filter() const {
     return resource_message_filter_.get();
   }
 
+  // See note in GetTaskRunner().
   base::MessageLoop* message_loop() const { return message_loop_; }
 
   // Returns the one child thread. Can only be called on the main thread.
   static ChildThreadImpl* current();
 
 #if defined(OS_ANDROID)
   // Called on Android's service thread to shutdown the main thread of this
   // process.
   static void ShutdownThread();
 #endif
@@ skipping 77 matching lines @@
   // Handles resource loads for this process.
   scoped_ptr<ResourceDispatcher> resource_dispatcher_;
 
   scoped_ptr<WebSocketDispatcher> websocket_dispatcher_;
 
   // The OnChannelError() callback was invoked - the channel is dead, don't
   // attempt to communicate.
   bool on_channel_error_called_;
 
   base::MessageLoop* message_loop_;
+  scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
 
   scoped_ptr<FileSystemDispatcher> file_system_dispatcher_;
 
   scoped_ptr<QuotaDispatcher> quota_dispatcher_;
 
   scoped_refptr<ChildHistogramMessageFilter> histogram_message_filter_;
 
   scoped_refptr<ChildResourceMessageFilter> resource_message_filter_;
 
   scoped_refptr<ServiceWorkerMessageFilter> service_worker_message_filter_;
@@ skipping 31 matching lines @@
 
 struct ChildThreadImpl::Options {
   ~Options();
 
   class Builder;
 
   std::string channel_name;
   bool use_mojo_channel;
   bool in_browser_process;
   std::vector<IPC::MessageFilter*> startup_filters;
+  scoped_refptr<base::SingleThreadTaskRunner> task_runner;
 
  private:
   Options();
 };
 
 class ChildThreadImpl::Options::Builder {
  public:
   Builder();
 
   Builder& InBrowserProcess(bool in_browser_process);
   Builder& UseMojoChannel(bool use_mojo_channel);
   Builder& WithChannelName(const std::string& channel_name);
   Builder& AddStartupFilter(IPC::MessageFilter* filter);
+  Builder& WithTaskRunner(
+      scoped_refptr<base::SingleThreadTaskRunner> task_runner);
 
   Options Build();
 
  private:
   struct Options options_;
 
   DISALLOW_COPY_AND_ASSIGN(Builder);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_CHILD_CHILD_THREAD_IMPL_H_